using System;
using System.Threading;
using MediaBrowser.Model.Tasks;
using Microsoft.Extensions.Logging;

namespace Emby.Server.Implementations.ScheduledTasks.Triggers;

/// <summary>
/// Represents a task trigger that fires everyday.
/// </summary>
public sealed class DailyTrigger : ITaskTrigger, IDisposable
{
    private readonly TimeSpan _timeOfDay;
    private Timer? _timer;
    private bool _disposed;

    /// <summary>
    /// Initializes a new instance of the <see cref="DailyTrigger"/> class.
    /// </summary>
    /// <param name="timeOfDay">The time of day to trigger the task to run.</param>
    /// <param name="taskOptions">The options of this task.</param>
    public DailyTrigger(TimeSpan timeOfDay, TaskOptions taskOptions)
    {
        _timeOfDay = timeOfDay;
        TaskOptions = taskOptions;
    }

    /// <inheritdoc />
    public event EventHandler<EventArgs>? Triggered;

    /// <inheritdoc />
    public TaskOptions TaskOptions { get; }

    /// <inheritdoc />
    public void Start(TaskResult? lastResult, ILogger logger, string taskName, bool isApplicationStartup)
    {
        DisposeTimer();

        var now = DateTime.Now;

        var triggerDate = now.TimeOfDay > _timeOfDay ? now.Date.AddDays(1) : now.Date;
        triggerDate = triggerDate.Add(_timeOfDay);

        var dueTime = triggerDate - now;

        logger.LogInformation("Daily trigger for {Task} set to fire at {TriggerDate:yyyy-MM-dd HH:mm:ss.fff zzz}, which is {DueTime:c} from now.", taskName, triggerDate, dueTime);

        _timer = new Timer(_ => OnTriggered(), null, dueTime, TimeSpan.FromMilliseconds(-1));
    }

    /// <inheritdoc />
    public void Stop()
    {
        DisposeTimer();
    }

    /// <summary>
    /// Disposes the timer.
    /// </summary>
    private void DisposeTimer()
    {
        _timer?.Dispose();
        _timer = null;
    }

    /// <summary>
    /// Called when [triggered].
    /// </summary>
    private void OnTriggered()
    {
        Triggered?.Invoke(this, EventArgs.Empty);
    }

    /// <inheritdoc />
    public void Dispose()
    {
        if (_disposed)
        {
            return;
        }

        DisposeTimer();

        _disposed = true;
    }
}
